Custom URL Schemes

One of the more interesting features provided by the SDK is
the ability for your application to use custom URL schemes to
launch other applications, and in turn, to register custom URL schemes of
its own. These schemes can be used to launch your application, either from
the browser or from another application on the device. Additionally, such
schemes are not just limited to launching the application; you can pass
additional information to your application via the URL.

Using Custom Schemes

Most of the built-in applications Apple provides respond to custom
URL schemes; for example, the Maps, Mail, YouTube, iTunes, and App Store
applications will all open in response to custom URLs. However, there
are also many established third-party applications with published URL
schemes that you can use in your own application.